My goodness, talk about a mixed bag here. This could be the craziest player profile I've seen in the last 5 or so years. Some guys have been just as unpredictable, but not with the ceiling Upton has, and not with the floor either. The spectrum is amazingly wide on this one. On to the numbers...
The first thing we need to look at it is steals, as this is where he's expected to acquire the majority of his value. In 2007 he had 22 steals, but had 56, 44, and 42 respectively in '06, '08, and '09. I think it's safe to call '07 an outlier, probably based on some sort of injury or an attempts issue. His wheels are just fine, so long as he gets on base, which is the 2nd issue.
His batting averages have been all over the spectrum as well, ranging from a career high .300 in '07 to a career low .241 last year. He makes very poor contact and his walk rate dropped HUGE last season. Big red flag. His BABIP is another peripheral with a strange trend. Last season he was getting hits around 31% of the time, down from 35% and 40% the previous two years. That should indicate this will be a correction year, but then again his hit rate was 31% in back to back seasons in the minors in '05 and '06. Where is his true number?
HR's is the last area of uncertainty. His total of 24 in '07 was the result of a 20% HR/FB rate. His best season otherwise is 7%.
I can honestly see Upton being a complete bust and falling off the fantasy radar. The problem is that I can just as easily see him being a first round pick next season. My best suggestion is draft for 40 steals and consider any batting average or power help a bonus. Hopefully we get a better idea of what he's made of this season.